1. Field of the Invention
The invention relates to an apparatus and a method concerning graphics processing in a computer system, and more particularly to an apparatus for supporting dual graphics adapters and method thereof.
2. Description of the Related Art
Computers have become of much more use in many activities with the advent of computer graphics displays which allow the presentation of not only numbers and text materials but pictures and graphs representing the meanings of those numbers and adding to the meaning of the text material.
Referring FIG. 1, in a conventional computer system, drawing work is sent from CPU 2 to an external graphics adapter 4 through chipset 1 and Accelerated Graphics Port (AGP) or Peripheral Component Interconnect (PCI) buses. The external graphics adapter 4 has an external graphics accelerator 41 for processing 2D and 3D graphics, and a local memory 42 acting as the graphics memory, or the video memory, of the graphics adapter 4. This graphics architecture reduces the overload of the processing recourse in CPU 2, which could be more concentrated on other matters except drawing pictures.
Nevertheless, because of progress in semiconductor manufacturing technology, it is a trend that the graphics adapter is embedded within an integrated chipset, and the local memory 42 is integrated into conventional system memory using the so-called Unified Memory Architecture (UMA). Therefore, referring to FIG. 2, drawing work is directly sent to the embedded graphics adapter 6 in the integrated chipset 6. The embedded graphics adapter 6 processes drawing works as the aforesaid external graphics adapter did. This integration dramatically reduces cost of a computer system as well as satisfies general users"" demand, because users do not have to spend extra cost to purchase a graphics card comprising an additional graphics adapter in their computers.
However, this integration is not reasonable and acceptable for a user who wants a the-state-of-the-art graphics accelerator, which processes 3D pictures faster, to play 3D games or to run 3D graphics programs. Getting a faster graphics card is one of many ways to upgrade an old computer system. Thus, the eager user usually purchases another graphics card with an additional state-of-the-art graphics accelerator in his computer system for more powerful 3D graphics acceleration functions.
Referring to FIG. 3, in order to avoid interference with the external graphics adapter 4 having the state-of-the-art graphics accelerator 41, the whole embedded graphics adapter 7 in the integrated chip must be disabled when an external graphics adapter exists. The embedded graphics adapter 7 thus is wasted.
Therefore, it is demanding that the computer system capable of supporting coexistence of external graphics adapter with embedded graphics adapter. With dual graphics adapters, a computer user can expand their desktop, run different programs on separate displays, even play some applications with multiple views, and each display can have a different resolution and color depth.
In view of the above, an objective of the invention is to provide an apparatus for supporting coexistence of an external graphics adapter with an embedded graphics adapter.
It is another objective of the invention that the graphics memory of the embedded graphics adapter is integrated into DRAM of the computer system, and CPU and embedded graphics adapter utilize PCI transaction to access graphics memory of embedded graphics adapter.
It is another objective of the invention that the embedded graphics adapter could be an AGP device while the external graphics adapter would be a PCI device, and vice versa.
To achieve the above objectives, the apparatus for supporting multiple graphics adapters in a computer system according to the invention includes an embedded graphics adapter, a corelogic, an AGP bridge and a PCI bridge. The embedded graphics adapter has an AGP interface and a PCI interface. The corelogic has a memory controller signally-connected to the graphics memory of the embedded graphics adapter. The AGP bridge is signally-connected with the AGP interface and the memory controller; and the PCI bridge is signally-connected with the PCI interface and the memory controller.
When an external AGP graphics adapter exists in the computer system, the embedded graphics adapter transfers data to the memory controller via the PCI interface and the PCI bridge using PCI transactions. On the other hand, when an external PCI graphics adapter exists in the computer system, the embedded graphics adapter transfers data to the memory controller via the AGP interface and the AGP bridge using AGP transactions.
When no external graphics adapter exists in the computer system, the embedded graphics adapter may act as an AGP device and transfer data to the memory controller via the AGP interface and the AGP bridge using AGP transactions.
The graphics memory of the embedded graphics adapter may be integrated into the DRAM of the computer system. The corelogic is capable of remapping graphics address and direct accessing the graphics memory for supporting the embedded graphics adapter and the external graphics adapter, respectively.
The invention also provides a method for supporting multiple graphics adapters in a computer system. Firstly, the status of the AGP slot and the PCI slot in the computer system is detected when the system boots up. Then, a slot-status parameter is set according to the detect result, and the mode of the embedded graphics adapter is determined according to the slot-status parameter.
The detecting and the setting may be performed by the BIOS of the computer system. The checking may be performed by the embedded graphics adapter or the BIOS of the computer system.
Additional objectives and advantages of the invention will be set forth in the description that follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the present invention may be realized and obtained by means of the instrumentalities and combinations of particularly pointed out in the appended claims.